The present invention relates to lifting devices and more particularly suction lifting devices for lifting and handling flat articles such as sheet lumber, glass sheet and the like.
Vacuum suction lifting devices. e.g., a vacuum chuck for lifting and handling sheets of steel, glass, resin, lumber, wall and roofing panels etc, operate by application of negative air pressure or vacuum to a sheet to pick up and transfer it thereby avoiding need to use mechanical components contacting the sheet that could impose harmful force on the sheet resulting in flawing or damaging the sheet and especially surfaces thereof.
Such vacuum devices are usually part of a larger system which includes components for identifying sizes and forms of the work pieces to be handled by means of sensors, or in some more advanced systems, using an image information processor. After recognizing the size and form of the work, the system then actuates vacuum cups, connecting pneumatic lines as well as other devices for handling the work pieces, this commonly being done with solenoid valves or other controlling devices embodied in the system. Vacuum pumps and vacuum ported devices also are necessary parts of the system. Known systems and lifters as used therewith have certain drawbacks and/or are unnecessarily complicated.
A known system such as an industrial robot disclosed in Japan Patent Bulletin 2-88193 comes with a blower under the vacuum cup so as to prevent a flexible and thin film workpiece, such as a sheet of paper, from falling from a transport arm holding the work at the vacuum cup. The blower is used to support the transport cycle of the arm by applying positive air pressure against the sheet supplementing the vacuum holding effect.
A suction cup device disclosed in Japan Patent Bulletin 2-29215 is equipped with a sliding shaft as a base which is free rotating. A suction cup is fixed at a protruding edge of the sliding shaft. A pneumatic passage can be formed inside the shaft to communicate with an activating port at the protruding edge. The structure and operation of this device is very complicated.
A piler system (loading/unloading system) disclosed in Japan Patent Bulletin 2-300014 is operated by input data, such as length and form of the workpiece, fed into a control system. The control after receiving these data selects appropriate suction cups enough to accomplish the job. During this step, a workpiece is held at a sensing position until the control system determines to where the workpiece should be transported to be processed at the next stage, which is in this instance, a loading position. This system also is very complicated.
A station system disclosed in Japan Patent Bulletin 2-305716 is for the sheet lumber industry. A size sensor in the system detects sizes of lumber sheet. After the control system is fed with size data, it selects and activates necessary suction cups required to handle the particular sheet lumber. The main mechanism for performing this operation comprises switch valves and a pneumatic power line network. The operating cycle is controlled by commands from the control system. Selected suction cups are then activated to pick up the work. This system is very complicated.
Less complicated and inexpensive, reliable system components such as the suction lifting device itself, thus represent a desirable need in connection with suction lifting of articles.